Power consumption of a power amplifier used in a radio base station tends to increase according to an increase in bandwidth of mobile and fixed radio communication, and therefore a high frequency amplifier for implementing high efficiency power amplification is required.
For the implementation of the high efficiency power amplification, a method of using a nonlinear operation of an amplification circuit is proposed as an example. A distortion compensation technology is indispensable for the nonlinear circuit using the method.
As an example of the distortion compensation method, a Pre-Distortion (PD) technique of reducing distortion of an entire system by adding a pre-distorted signal component such as reverse characteristics of nonlinearity of an amplifier with a nonlinear circuit to a transmission signal has been known. A Digital Pre-Distortion (DPD) technique has been known as a representative example of compensating for power distortion through the pre-distortion technique.
Technologies of compensating for distortion of a power amplifier through the pre-distortion method are disclosed in Japanese patent publication No. 2009-111958 (hereinafter, referred to as patent document 1) and No. 2008-258713 (hereinafter, referred to as patent document 2).